Etymology:

This expression was first used by William Shakespeare in his famous tragedy Othello in the 17th century. Back in those days, it was in the culture that a young lady tied a ribbon around her arm for her boyfriend. On the other hand, the boyfriend then wore the ribbon on his sleeve which is one of the obvious parts of the clothing. The ribbon was used to reveal the feelings of the boyfriend to everyone. In the present world, the idiom “wearing your heart on your sleeve” is used to reveal the feeling of love.